A new full-protected control mode to drive piezoelectric transformers in DC-DC converters

Due to their high power density and their low EMI generation, piezoelectric transformers (PTs) are an attractive solution to replace magnetic transformers in AC/DC power converters. However, this substitution implies changes in the power topology and the control strategy because of the very frequency-dependent behavior of PTs, and their capacitive features. In previous works, some power topologies have been presented to deal with this new component, and frequency modulation has been assumed as the natural way to control the output voltage, sometimes in combination with pulse width modulation (PWM), to achieve both line and load regulation. In the frame of a particular application, this paper presents a new control method for PT-based converters. This control method is very simple to design, requires very few components and regulates the output voltage maintaining constant the frequency and the pulse width, trying to obtain the best characteristics from the piezoelectric device.